1. Field of the Invention
The present invention relates to an actuator for a speed governor of an elevator system, and also to a speed governor equipped with such an actuator.
2. Description of Related Art
Speed governors for elevator systems initiate emergency measures, for example the activation of a safety stop device, if an actuation speed is exceeded.
DE 34 46 337 A1 discloses a speed governor for an elevator system that actuates the safety stop of the elevator cabin if the actuation speed is exceeded. The speed governor comprises a cable sheave that is connected to the elevator cabin by means of a cable loop and is set in rotation when the elevator cabin moves. The cable sheave carries flyweights that are connected to rotatably mounted eccentric cams. When the cable sheave rotates the flyweights swing outwards, the eccentric cams thereby being rotated or deflected so that they press against a brake wheel if the actuation speed is exceeded. In this way the cable sheave and, as a result of the traction of its cable groove, the cable looped around it are braked, the safety stop device thereby being actuated.
In addition, speed governors are known in which, instead of a brake wheel, an actuator wheel is provided, which, when the actuation speed is exceeded, is engaged by the coupling means and caused to co-rotate. Due to the rotation of the actuator wheel a cable brake for the cable looped around the cable sheave is then actuated, whereby in turn a safety stop device on the elevator cabin is actuated. Such a speed governor is marketed for example under the reference number OL100 by the Wittur company.
The speed governors known in the prior art have the disadvantage that the cooperation of cable sheave, flyweights, coupling means and actuator and brake wheel involves a large number of individual components, which are all subject to specific tolerance requirements. The previous solutions require high manufacturing tolerances, since they are structurally over-determined and have a degree of redundancy. This redundancy of the construction can lead to malfunctions and a high degree of wear. The overall system is consequently relatively expensive, since in the production certain minimum tolerances for the individual components have to be maintained. This also arises from the symmetrical construction, i.e., individual components such as for example flyweights and coupling means are as a rule provided at least in duplicate, so that the tolerances of an individual component as well as tolerances involving several components play a role. As a result, in particular, the production and maintenance proves to be difficult since not only structural components have to be found that lie within the prescribed tolerance limits, but their dimensions also have to be matched to one another. Since an elevator is normally subjected to large forces and speeds, the individual components have to be manufactured from rigid and solid materials, such as for example steel, that have a very high spring constant, so that the permissible tolerances are relatively small. Owing to the large spring constants large forces act, this means that the components, bearings and bolts have to be robustly designed.
It is therefore desirable to provide an actuator for a speed governor that is simpler and therefore less expensive to produce, in which the actuation behaviour must not however be adversely affected.